Read the cryptonomicon! It's a really good intro to a lot of stuff that's harder to teach. It's also not too technical, which might help you get into things.

For secure devices you should be worried about:

* Entropy

* Radio signals (produced by your electronics)

* Physical opening of devices (this happens)
* Lightweight algorithms.

Sorry to have any specific papers or anything, I think others are better capable of recommendations. Have fun out there.